Mezaark was apparently recruited by Rogles time before the events of the first game.
In the prologue (trailer) of Valis I, Mezaark attacked Yuuko along with many other monsters but was easily defeated by her. During the game, Rogles gave him a Phantasm jewel and sent him to control the Ruins Area in Dream world near Vanity city. As Yuuko had to collect all the Phantasm jewels to enter Rogles's castle and save Valia, she went to this area first and fought Mezaark. He used all his forms to attack Yuuko but lost and died anyways. The Valis warrior took his Phantasm jewel afterwards.
There isn't much details about Mezaark's personality. As he was seen in the trailer and the game, his personality is shown to be bestial and wild, making questionable if Mezaark is actually an intelligent life form.
Mezaark can use his claws to attack but can also shot energy balls from his mouth. In his second form, he can fly in different patterns and spread the energy balls from the air.
Mezaark appeared in the Famicom/NES version of Valis I (in the trailer and the game itself) as the first boss guarding the Ruins Area. Beating him gives the player the first Phantasm jewel and the access to the Forest area.
- Although Mezaark's colour is shown as clear pink in the trailer, his sprite in the game is coloured as dark red. His eye is also coloured blue, possibly due to graphical limitations.
- Also, Mezaark is shown as a bulky and fat monster in the trailer, while in the games, he has skeletal details in his appearance.
- If the trailer is taken as a prequel to the game, It's possible that Mezaark's skeletal appearance in the game could be caused by some type of regeneration as he was cut in half by Yuuko during the trailer.
- In the trailer's scene where Yuuko cuts in half many monsters including Mezaark, there is another Mezaark she cuts after killing the first, meaning that there were more than one Mezaark and that one of them possibly didn't survive.
- Mezaark is the only first boss (in combat order) from all versions of Valis I to haven't been fought in the Tokyo city area.
- Mezaark is also the only boss from the Famicom/NES version of Valis I to have more than one form.